AJP - Gastrointestinal and Liver Physiology, Vol 242, Issue 3 243-G249, Copyright © 1982 by American Physiological Society
Mucosal gastrin receptor. VII. Up- and downregulation
G. R. Speir, K. Takeuchi, W. Peitsch and L. R. Johnson
A series of experiments were performed to examine the long-term
upregulation of the gastrin receptor and to explore the possibility of a
short-term down regulation with regard to the time course of the trophic
action of gastrin. Vagotomy or fasting was used to examine upregulation.
Elevated serum gastrin levels observed postvagotomy are accompanied by an
increase in gastrin binding capacity. Conversely, fasting caused a decline
in serum gastrin and receptor levels; refeeding restored both values to
normal levels. Cycloheximide was used to study the role of protein
synthesis in the upregulation of gastrin receptors in vagotomized and refed
rats, and it prevented the rise of gastrin binding capacity to either
normal or above-normal values. This indicates that protein synthesis may
play an integral part of receptor upregulation. Following the injection of
gastrin-17, there was a short-term induction of downregulation. These
results coupled with the maximal reduction of gastrin receptor 3 h after
cycloheximide injection indicate that the gastrin receptor has a short
half-life. Following the gastrin receptor interaction, the cellular
response occurs at discrete periods and manifests itself as both down- and
upregulation.
